{
  "id": "2106.01928",
  "version": "v1",
  "published": "2021-06-03T15:28:43.000Z",
  "updated": "2021-06-03T15:28:43.000Z",
  "title": "The SAMI Galaxy Survey: Trends in [α/Fe] as a Function of Morphology and Environment",
  "authors": [
    "Peter J. Watson",
    "Roger L. Davies",
    "Sarah Brough",
    "Scott M. Croom",
    "Francesco D'Eugenio",
    "Karl Glazebrook",
    "Brent Groves",
    "Ángel R. López-Sánchez",
    "Jesse van de Sande",
    "Nicholas Scott",
    "Sam P. Vaughan",
    "Jakob Walcher",
    "Joss Bland-Hawthorn",
    "Julia J. Bryant",
    "Michael Goodwin",
    "Jon S. Lawrence",
    "Nuria P. F. Lorente",
    "Matt S. Owers",
    "Samuel Richards"
  ],
  "comment": "15 pages, 9 figures",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "We present a new set of index-based measurements of [$\\alpha$/Fe] for a sample of 2093 galaxies in the SAMI Galaxy Survey. Following earlier work, we fit a global relation between [$\\alpha$/Fe] and the galaxy velocity dispersion $\\sigma$ for red sequence galaxies, [$\\alpha$/Fe]=(0.378$\\pm$0.009)log($\\sigma$/100)+(0.155$\\pm$0.003). We observe a correlation between the residuals and the local environmental surface density, whereas no such relation exists for blue cloud galaxies. Returning to the full sample, we find that galaxies in high-density environments are $\\alpha$-enhanced by up to 0.06 dex at galaxy velocity dispersions $\\sigma$<100 km/s, compared to their counterparts in low-density environments. This $\\alpha$-enhancement includes a dependence on morphology, with an offset of 0.057$\\pm$0.014 dex for ellipticals, and decreasing along the Hubble sequence towards spirals, with an offset of 0.019$\\pm$0.014 dex. Conversely, for galaxies with $\\sigma$>100 km/s in low-density environments, the [$\\alpha$/Fe]-$\\sigma$ relation is consistent across all morphological types earlier than Sc. At low galaxy velocity dispersion and controlling for morphology, we therefore estimate that star formation in galaxies in high-density environments is truncated $\\sim$1 Gyr earlier, compared to those in low-density environments. At the highest velocity dispersions, $\\sigma$>200 km/s, we find no difference in the [$\\alpha$/Fe] ratio of galaxies earlier than Sc. Hence, we infer that the integrated star-formation timescales cannot differ substantially between high-$\\sigma$ galaxies across varied environments, supporting the relative dominance of mass-based quenching mechanisms at the highest mass scales.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2021-06-03T15:28:43.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "sami galaxy survey",
      "low-density environments",
      "morphology",
      "high-density environments",
      "local environmental surface density"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 15,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}